Browsing by Subject "Transport"
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Item A T-Matrix Approach to Heavy Quark Interaction with Thermal Gluons in a Quark Gluon Plasma(2012-10-19) Huggins, KyleThe interactions of heavy quarks within the Quark Gluon Plasma (QGP) are interpreted utilizing an elastic, thermodynamic, 2-body T-matrix in order to calculate drag coefficients of heavy-quark systems derived from a Fokker-Planck equation. A spacelike momentum constraint is employed and produces an effective, color dependent potential with the addition of relativistic factors motivated by the appropriate Feynman diagrams. Hard Thermal Loop (HTL) corrections are interpreted in the context of a finite temperature quark-gluon system, allowing a non-perturbative determination of the gluon's contribution to the drag coefficient. An enhancement of the relaxation rate of ~2 is observed at low momenta, leading to an enhancement of the overall relaxation rate of 20%, while the high-p limit approaches a perturbative level. The importance of a nonperturbative treatment of the QGP to reproduce the dynamical drag coefficient is illustrated.Item Adaptive discrete-ordinates algorithms and strategies(2009-05-15) Stone, Joseph CarlyleThe approaches for discretizing the direction variable in particle transport calculations are the discrete-ordinates method and function-expansion methods. Both approaches are limited if the transport solution is not smooth. Angular discretization errors in the discrete-ordinates method arise from the inability of a given quadrature set to accurately perform the needed integrals over the direction ("angular") domain. We propose that an adaptive discrete-ordinate algorithm will be useful in many problems of practical interest. We start with a "base quadrature set" and add quadrature points as needed in order to resolve the angular flux function. We compare an interpolated angular-flux value against a calculated value. If the values are within a user specified tolerance, the point is not added; otherwise it is. Upon the addition of a point we must recalculate weights. Our interpolatory functions map angular-flux values at the quadrature directions to a continuous function that can be evaluated at any direction. We force our quadrature weights to be consistent with these functions in the sense that the quadrature integral of the angular flux is the exact integral of the interpolatory function (a finite-element methodology that determines coefficients by collocation instead of the usual weightedresidual procedure). We demonstrate our approach in two-dimensional Cartesian geometry, focusing on the azimuthal direction The interpolative methods we test are simple linear, linear in sine and cosine, an Abu-Shumays ?base? quadrature with a simple linear adaptive and an Abu-Shumays ?base? quadrature with a linear in sine and cosine adaptive. In the latter two methods the local refinement does not reduce the ability of the base set to integrate high-order spherical harmonics (important in problems with highly anisotropic scattering). We utilize a variety of one-group test problems to demonstrate that in all cases, angular discretization errors (including "ray effects") can be eliminated to whatever tolerance the user requests. We further demonstrate through detailed quantitative analysis that local refinement does indeed produce a more efficient placement of unknowns. We conclude that this work introduces a very promising approach to a long-standing problem in deterministic transport, and we believe it will lead to fruitful avenues of further investigation.Item Adaptive discrete-ordinates algorithms and strategies(Texas A&M University, 2008-10-10) Stone, Joseph CarlyleThe approaches for discretizing the direction variable in particle transport calculations are the discrete-ordinates method and function-expansion methods. Both approaches are limited if the transport solution is not smooth. Angular discretization errors in the discrete-ordinates method arise from the inability of a given quadrature set to accurately perform the needed integrals over the direction ("angular") domain. We propose that an adaptive discrete-ordinate algorithm will be useful in many problems of practical interest. We start with a "base quadrature set" and add quadrature points as needed in order to resolve the angular flux function. We compare an interpolated angular-flux value against a calculated value. If the values are within a user specified tolerance, the point is not added; otherwise it is. Upon the addition of a point we must recalculate weights. Our interpolatory functions map angular-flux values at the quadrature directions to a continuous function that can be evaluated at any direction. We force our quadrature weights to be consistent with these functions in the sense that the quadrature integral of the angular flux is the exact integral of the interpolatory function (a finite-element methodology that determines coefficients by collocation instead of the usual weightedresidual procedure). We demonstrate our approach in two-dimensional Cartesian geometry, focusing on the azimuthal direction The interpolative methods we test are simple linear, linear in sine and cosine, an Abu-Shumays ? base? quadrature with a simple linear adaptive and an Abu-Shumays ? base? quadrature with a linear in sine and cosine adaptive. In the latter two methods the local refinement does not reduce the ability of the base set to integrate high-order spherical harmonics (important in problems with highly anisotropic scattering). We utilize a variety of one-group test problems to demonstrate that in all cases, angular discretization errors (including "ray effects") can be eliminated to whatever tolerance the user requests. We further demonstrate through detailed quantitative analysis that local refinement does indeed produce a more efficient placement of unknowns. We conclude that this work introduces a very promising approach to a long-standing problem in deterministic transport, and we believe it will lead to fruitful avenues of further investigation.Item Characterization of a Stochastic Procedure for the Generation and Transport of Fission Fragments within Nuclear Fuels(2013-04-15) Hackemack, Michael WayneWith the ever-increasing demands of the nuclear power community to extend fuel cycles and overall core-lifetimes in a safe and economic manner, it is becoming more necessary to extend the working knowledge of nuclear fuel performance. From the atomistic to the macroscopic level, great morphological changes occur within the fuel over its lifetime. The main initial damaging events produced by fuel recoils from fast neutrons and fission fragment spiking leads to the onset of grain growths and fuel restructuring. Therefore, it is desirable to have a more detailed understanding of the initial events leading to fuel morphology changes at the atomistic level. However, this is difficult to achieve with the fission fragments due to the wide variability of their species (charge, mass, and energy) and the large averaging of their relative yields in the nuclear data files. This work is our first iteration at developing a general methodology to characterize a procedure, based on Monte Carlo principles, for generating individual fission event result channels and analyzing their specific response in the fuel. We utilized the nuclear reaction simulation tool, TALYS, to generate energy-dependent fission fragment yield distributions for different fissile/fissionable isotopes. These distributions can then be used in conjunction with fuel isotopics and a neutron energy spectrum to generate a fission-reaction-rate-averaged distribution of the fission fragment yields. We then used Monte Carlo sampling to generate the result channels from individual fission events, using the Q-value of the prompt fission system to either accept or reject. The simulation tool: Transport of Ions in Matter (TRIM) was used to characterize the general response of the fission fragment species within Uranium Dioxide (UO2), including the range, energy loss, displacements, recoils, etc. These responses were then correlated which allowed for the quick calculation of the response of the individual fission fragment species generated from the Monte Carlo sampling. As an example of this strategy, we calculated the response on a PWR fuel pin where MCNP was used to generate a high-fidelity neutron energy spectrum.Item Computational modeling of transport through polymer membranes and globular proteins(2012-08) Jiang, Yingying, doctor of chemical engineering; Sanchez, Isaac C., 1941-; Paul, Donald R.; Freeman, Benny D.; Truskett, Thomas M.; Elber, RonWithin a polymer thin film, free-volume elements have a wide range of size and topology. This broad range of free-volume element sizes determines the ability for a polymer to perform molecular separations. Herein, the free volume and transport properties (diffusion, permeability, and selectivity) in both rubbery and glassy polymers were simulated using fully atomistic models. Extension of the computational tool to study the void structure in proteins is also included in this thesis. Six permeable thermally rearranged (TR) polymers and their precursors were studied. Using atomistic models, cavity size (free volume) distributions determined by a combination of molecular dynamics and Monte Carlo methods were consistent with experimental observation that TR polymers are more permeable than their precursors. The cavity size distributions determined by simulation were also consistent with free volume distributions determined by positron annihilation lifetime spectroscopy. The diffusion, solubility and permeation of gases in TR polymers and their precursors were also simulated at 308 K, with results that agree qualitatively with experimental data. A new hybrid Monte Carlo/Molecular Dynamics method is developed for estimating the slow diffusion processes of light gases transporting in glassy polymers. Diffusion coefficients, as small as 10⁻⁵ to 10⁻⁹ cm²/s are estimated for penetrants in four different polymers at 298 K. In all cases, agreement between literature experimental data and values obtained from the fast hybrid molecular dynamics method ranges from good to excellent. A new technique is developed using Monte Carlo methods to characterize the cavity size distribution and surface atoms in globular proteins. New statistical metrics have been defined for the structural characterization of globular proteins. Some of these metrics include volume, surface area, asymmetry ratio, interior cavity size distribution, and the identification of percolation channels. Wild-type (WT) myoglobin (Mb) and 5 Mb mutants have been studied in this research as examples. An analysis of cavity statistics provides an efficient method to quantify local properties such as packing density and transport pathways. The average cavity sizes of WT Mb and its mutants are around 4.0-5.0 Å.Item Development of environmental and oceanographic real-time assessment system for the near-shore environment(Texas A&M University, 2006-08-16) Ojo, Temitope O.The coupling of real-time measurements and numerical models will be important in overcoming the challenges in environmental and oceanographic assessments in surface waters. Continuous monitoring will take advantage of current state-of-the-art in sensor development, remote sensing technology. The numerical modeling tools available exist in many different forms and varying levels of complexity from depth integrated one-dimensional (1-D) models to full three-dimensional (3-D) models. Common to all are the constraints and forcing required in driving the models. These include hydrodynamic and barometric information, which are relatively difficult to obtain given the time scale of the bio-chemical and physical processes governing the fate and transport of the constituents of interest. This study is focused on the development of a framework that couples real-time measurements and numerical simulation for tracking constituents in surface waters. The parameterization of the mixing and turbulent diffusion impacts the formulation of the constituent-transport governing equations to the extent that the numerical model is being driven by near real-time observations of hydrodynamic data and the consequent evaluation of model coefficients. The effects of shear-augmented diffusion processes in shallow embayment and near-shore waters are investigated in order to develop algorithms for obtaining a shear diffusion coefficient, Ke from shear-current measurements and turbulent diffusion-coefficient, Kz measured by the auto-correlation function, Rτ of the velocity time-series. Typically, the diffusion coefficients are measured through tracer experiments as determined by the time rate of change of the variance of a growing patch (K = ?? dσ2 /dt), which introduces the concept of diffusion length-scale (or time-scale). In this study, the dye-tracer experiment was used, not so much in the context of evaluation of a diffusion coefficient, but within a modeling framework to validate a numerical scheme driven by real-time hydrodynamic observations. Overall, the effect of shear-currents in shallow wind-driven estuaries is studied using a prototype bay typical of the Texas Gulf-coast. A numerical model was developed and used in testing these hypotheses through a series of dye-tracer experiments under varying meteorological conditions.Item Dynamic response of polycrystalline organic thin film transistors(2010-05) Cobb, Brian Hardy, 1982-; Dodabalapur, Ananth, 1963-; Tutuc, Emanuel; Bank, Seth; Register, Leonard F.; Li, XiaoqinIn this dissertation, charge transport through organic field effect transistors is explored. In particular, small molecule-based devices consisting of Pentacene semiconducting thin films are investigated. The relationship between electric field and carrier velocity is explored over a wide range of electric fields. These velocities are then compared to directly measured velocities measured from transient measurements. New device structures are fabricated in order to provide low voltage operation, along with a method to stabilize the output response and reduce bias stress effects. A novel method is proposed to investigate the dynamics of trap response rate in highly localized systems through the characterization of the large signal frequency response of a vii device. This method is then used to gain greater insight into bias stress effects and the ability of a transistor to respond to a rapidly changing input. A greater understanding of the transport of charge through a channel is obtained, leading to a more realistic picture in which a single mobility value is an insufficient description of carrier transport through a material.Item Effect of duration of transport on indicators of stress in lambs(Texas A&M University, 2007-04-25) Krawczel, Peter DownsRecommendations for the transportation of lambs from a European Commission, which required rest stops of 6 or 24 h, every 8 h, were evaluated for efficacy of reducing stress indicators using Rambouillet x Suffolk lambs (17.6 ???? 0.5 kg). The lambs were randomly assigned to one of three groups: 1) transported for 22 h (Continuous; n = 15); 2) transported for 8 h, unloaded and rested for 6 h, transported for 8 h, unloaded and rested for 24 h, transported for 6 h (Rested, n = 15); and 3) Control, which remained in home pasture throughout the study (n = 16). The rest stops were off-trailer; a different pen was used for each; and, a limited amount of grain and ad lib hay and water were provided. Mean temperature in the trailer during the study was 28.4???? C with a range of 18.2???? C to 39.6???? C. Food deprivation in the Continuous lambs was reflected by a decrease in plasma glucose (P < 0.001) and an increase in blood urea nitrogen (P < 0.001), creatinine (P < 0.02) and total bilirubin (P < 0.001) relative to the Rested or the Control lambs. Electrolytes varied within and between all three treatments (P < 0.05), but no distinct pattern indicating dehydration was evident. Serum concentrations of cortisol were greater (P < 0.05) in Continuous lambs than in the Control lambs at 14 h and both the Continuous and Rested lambs had higher concentrations of cortisol (P < 0.05) compared to the Control lambs at 22 h. Plasma IgG antibody response to ovalbumin was suppressed (P < 0.05) in the Continuous and Rested lambs compared to the Control lambs. Lambs in both transported treatments ate grain immediately upon release into the rest pens and drinking occurred following the food consumption. The Continuous lambs lost a greater (P < 0.05) amount of initial BW at the conclusion of transport compared to the Rested lambs and had a lower BW (P < 0.05) than the Rested and Control lambs 8 d after the start of transport. Rest stops improved welfare by reducing physical stress of food deprivation and eliminating BW loss during transport. However, rest stops failed to completely alleviate immunosuppression and 52 h were required to complete the otherwise 22 h long trip. The additional costs of providing the benefits of the rest stops should be examined before these regulations are widely implemented.Item Effects of Acute and Chronic Stress on Immune- and Inflammatory-response Gene Expression in Beef Calves(2012-02-14) Terrill, CooperTransport stress research has shown correlations among stress, morbidity, and mortality in calves subjected to the traditional U.S. market system, indicating the possibility of compromised immune function. The objective of this study was to determine if expression of specific immune and inflammatory response genes differed between calves that were subjected to either an acute stress (AS, handled and weaned for 1.5 h) or a chronic stress (CS, weaned, handled and transported for 3 to 4 d). Two groups of forty calves, Bos taurus (n = 20) and crossbred calves (n = 20), weighing 181 kg to 250 kg were used in each of two trials. Jugular veni-puncture blood samples (9 ml) were collected from AS calves 1.5 h after the start of handling and separation from their dam. Samples were collected from CS calves during processing after arrival at a north Texas feed lot. RNA for gene expression analysis was extracted from peripheral blood leukocytes obtained from blood samples by a filtration method. During the second trial, the filtrate was centrifuged for measurement of plasma cortisol. A diagonal covariance mixed model ANOVA was used to determine effects of treatment, breed, and breed by treatment interaction on cortisol concentrations. Expression values for each gene were analyzed using linear models that considered the effects of treatment (AS and CS) and breed (Bos taurus and crossbred calves) comparing each trial separately. Mean plasma cortisol concentrations did not differ between AS (16.40 +/- 1.08 ng/ml) and CS calves (18.06 +/- 1.14 ng/ml) (P > 0.296). The interaction of effects was detected for 2 genes in Trial 1, and 3 genes in Trial 2 (P < 0.029). Breed was influential for 5 genes in both Trial 1 and 2 (P < 0.046). Significant differences were found in relative quantification for 30 genes in Trial 1 and 36 genes in Trial 2, in which CS calves had greater expression than AS calves (P < 0.047). Fifteen of those genes were common between the two trials with mean treatment differences of RQ values from the 15 genes ranging from 0.309 to 913.19, excluding outliers. Similar elevated cortisol concentrations in both the AS and CS calves indicated that both groups experienced significant stress. However, changes in gene expression differences were greater in the calves subjected to CS, indicating that gene expression may be more useful than cortisol for identifying detrimental long-term stress.Item Electostatic plasma edge turbulence and anomalous transport in SOL plasmas(2014-08) Meyerson, Dmitry; Gentle, Kenneth W.; Waelbroeck, F.Controlling the scrape-off layer (SOL) properties in order to limit divertor erosion and extend component lifetime will be crucial to successful operation of ITER and devices that follow, where intermittent thermal loads on the order of GW/m² are expected. Steady state transport in the edge region is generally turbulent with large, order unity, fluctuations and is convection dominated. Owing to the success of the past fifty years of progress in magnetically confining hot plasmas, in this work we examine convective transport phenomena in the SOL that occur in the relatively "slow", drift-ordered fluid limit, most applicable to plasmas near MHD equilibrium. Diamagnetic charge separation in an inhomogeneous magnetic field is the principal energy transfer mechanism powering turbulence and convective transport examined in this work. Two possibilities are explored for controlling SOL conditions. In chapter 2 we review basic physics underlying the equations used to model interchange turbulence in the SOL and use a subset of equations that includes electron temperature and externally applied potential bias to examine the possibility of suppressing interchange driven turbulence in the Texas Helimak. Simulated scans in E₀×B₀ flow shear, driven by changes in the potential bias on the endplates appears to alter turbulence levels as measured by the mean amplitude of fluctuations. In broad agreement with experiment negative biasing generally decreases the fluctuation amplitude. Interaction between flow shear and interchange instability appears to be important, with the interchange rate forming a natural pivot point for observed shear rates. In chapter 3 we examine the possibility of resonant magnetic perturbations (RMPs) or more generally magnetic field-line chaos to decrease the maximum particle flux incident on the divertor. Naturally occurring error fields as well as RMPs applied for stability control are known to cause magnetic field-line chaos in the SOL region of tokamaks. In chapter 3 2D simulations are used to investigate the effect of the field-line chaos on the SOL and in particular on its width and peak particle flux. The chaos enters the SOL dynamics through the connection length, which is evaluated using a Poincaré map. The variation of experimentally relevant quantities, such as the SOL gradient length scale and the intermittency of the particle flux in the SOL, is described as a function of the strength of the magnetic perturbation. It is found that the effect of the chaos is to broaden the profile of the sheath-loss coefficient, which is proportional to the inverse connection length. That is, the SOL transport in a chaotic field is equivalent to that in a model where the sheathloss coefficient is replaced by its average over the unperturbed flux surfaces. Both fully chaotic and the flux-surface averaged approximation of RMP application significantly lower maximum parallel particle flux incident on the divertor.Item Experimental measurement of energy transport in tokamak plasmas(2010-08) Meyerson, Dmitry; Gentle, Kenneth W.; Horton, WendellA tokamak plasma near equilibrium can be perturbed with modulated power sources, such as modulated electron cyclotron heating, or repeated cold pulse application. Temperature response to cyclical changes in profiles parameters that are induced by modulated power deposition can be used to test theoretical transport models as well as improve experimental phenomenology used to optimize tokamak performance. The goal of this document to discuss some methods of analyzing electron temperature data in the context of energy transport. Specific experiments are considered in order to demonstrate the methods discussed, as well as to examine the electron energy transport properties of these shots. Electron cyclotron emission provides a convenient way to probe electron temperature for plasmas in thermal equilibrium. We can show that in tokamak devices,barring harmonic overlap, we can associate a particular frequency with a particular location in a tokamak, by carefully selecting the detection frequency and line of sight of the responsible antenna. ECE radiometers typically measure temperature at tens of locations at a time with a spatial resolution on the order of a few centimeters. Tracking the evolution of electron energy flux depends on careful analysis of the resulting data. The most straightforward way to analyze temperature perturbations is to simply consider various harmonics of the driving source and consider the corresponding harmonics in the temperature. We can analyze the phase and amplitude of the response to find the effective phase velocity of the perturbation which can in turn be related to parameters in the selected heat flux model. The most common example is to determine , the diffusion coefficient that appears in the linearized energy transport equation. The advantages and limitation of this method will be discussed in detail in Section 3. A more involved approach involves using the perturbed temperature data to compute modulated heat flux at any given point in the perturbation cycle, rather than using the temperature data directly. As before the heat flux can then be related to measured profile parameters and theoretical predictions. The advantages and limitations of this approach will be discussed in more detail. Both of the mentioned analysis methods are used to probe electron energy transport in a quiescent H mode (QH mode) shot conducted at DIIID. The nature of the internal transport barrier that is present in the shot is considered in light of the results.Item Experimental study on transport phenomenon during deep fat frying of chicken nuggets(2011-05) Lalam, Sravan; Takhar, Pawan S.; Thompson, Leslie D.; Alvarado, Christine Z.Two important factors affecting oil uptake of food products during deep fat frying (DFF) are water content and pressure development. In the past frying studies, pressure has not been measured physically but was calculated using computer models, which has resulted in some disagreements in the literature about its magnitude. The present study tries to explain the complex mass transfer mechanisms (fat uptake and moisture loss) taking place during DFF with respect to real time pressure variations inside chicken nuggets. The first objective of this study was to measure the pressure changes inside nuggets during frying by using a fiber optics sensor (FISO Technologies Inc, Québec, Canada). The second objective was to perform fat and moisture analysis for methylcellulose (MC) and control nuggets at different frying times and temperatures. The third objective was to visualize the microstructure in the core, crust and cross-section of chicken nuggets using scanning electron microscopy. The fourth objective was to visualize the oil uptake by the nuggets by frying them for various times in oil containing a fat-soluble dye (Sudan Red) and then observing them under light microscope. Breaded chicken nuggets were made with and without 5% MC added to predust. All the frying experiments were performed at two temperatures (175ºC and 190ºF) for 0, 30, 60, 120 and 240 sec. The gauge pressure increased rapidly above the atmospheric pressure immediately after the nuggets were introduced into hot oil. This was expected due to sudden moisture flash-off. As the temperature of the nugget increased, the pressure inside the nugget decreased to negative values (suction). As the nugget was removed from the fryer after 240 sec (post-frying cooling phase), the pressure decreased further for another 2 to 3 min. The negative pressure values caused rapid absorption of surface oil. During the post-frying cooling phase, the pressure tends to reach an equilibrium negative value and then starts rising back to 0 bars (ambient pressure) in 2 to 3 hour. The highest value of pressure was 0.0018 bars and the lowest was -0.19 bars. The MC-coated nuggets had lower fat uptake and higher moisture retention when compared to control nuggets in the core and crust regions for both frying temperatures. From the scanning microscopic analysis, control nuggets had higher levels of randomness in the crust, core and meat layers in terms of microstructure development, surface texture, rigidity and pore sizes when compared to MC-coated nuggets. With an increase in frying temperature, the nuggets had more surface damage and increased complexity of microstructure for both treatment and control nuggets. The nuggets fried in dyed oil showed oil penetration only from 1 mm to 4 mm into the meat layer from the crust. This implied that the oil uptake in the frying process was a surface phenomenon when observed under the light microscope. The present results provided scarce of real time pressure variation data during DFF with respect to the simultaneous mass transfer processes taking place. This will aid in understanding and elucidating of the oil uptake mechanisms, oil distribution, microstructure development and other parameters needed for optimizing the frying process to obtain healthier, low fat fried foods.Item Fundamental water and ion transport characterization of sulfonated polysulfone desalination materials(2014-08) Cook, Joseph Reuben; Freeman, B. D. (Benny D.)Sulfonated polysulfones BisAS and BPS were fabricated into dense polymer films, and their water and ion transport properties were systematically characterized. Fundamental NaCl and water transport properties were correlated with polymer chemistry, and water and NaCl permeability were found to increase with degree of sulfonation due to the increasing polymer water content. The BisAS backbone structure was found to result in greater water uptake, increasing water and salt permeability, though the polysulfones show evidence of sensitivity to the thermal casting process as well. Additionally, water and ion permeability and sorption values were determined for select polymers when exposed to a feed consisting of mixtures of monovalent and divalent cation salts. The divalent cations were found to sorb into the polymer much more favorably than the monovalent sodium, similarly to charged materials found in the literature. The sodium permeability of sulfonated polysulfones was found to increase in the presence of divalent cations by ratios of 2 to 5 times more than when exposed to an equivalent increase in feed charge concentration of monovalent cations. It has been hypothesized the more strongly charged divalent cations are neutralizing the sulfonate charges and suppressing Donnan exclusionary effects that reduce salt transport in charged polymers.Item Generation, stability, and transport of nanoparticle-stabilized oil-in-water emulsions in porous media(2014-05) Gabel, Scott Thomas; Bryant, Steven L.; Huh, ChunThe ability of nanoparticles to stabilize oil/water emulsions provides many interesting opportunities for the petroleum industry. Emulsions can be used as a displacing fluid for enhanced oil recovery to improve sweep efficiencies. Emulsions can be used to improve conformance control by effectively blocking thief zones in reservoirs with a high degree of heterogeneity. As shown in this thesis emulsions can be used to deliver fluids that contact and mobilize residual oil. It is imperative to understand emulsion behavior in porous media for design purposes in enhanced or improved oil recovery processes involving emulsions. Nanoparticle-stabilized oil-in-water emulsions were continuously generated by co-injecting aqueous nanoparticle dispersion and oil through a beadpack. There exists a critical shear rate below which a stable emulsion will not be generated. The critical shear rate increased with decreasing bead size. Above the critical shear rate, the droplet size of the generated emulsion was a function of shear rate and decreased with increasing shear rate. The stable emulsions were characterized by their droplet size and rheology. The emulsion viscosity was highly dependent upon droplet size and not the bulk oil viscosity in the emulsion. The emulsions were highly shear thinning and emulsions with smaller droplets were more viscous than emulsions with larger droplets. Highly stable emulsions that were generated by co-injection were collected, separated from excess phase(s) and injected into beadpacks. In most experiments the injected emulsion coalesced into the bulk fluids. Whether the bulk fluids generated a new emulsion in the bead pack depended on the shear rate, bead size, and initial saturation of the beadpack. Different beadpack experiments showed the transition from one flow regime to a second flow regime as the slow movement of a coalescence/regeneration front propagated through the beadpack. Coreflood experiments confirmed the mechanisms hypothesized for the beadpack emulsion injection experiments. When a stable emulsion was injected the effluent emulsion rheology and droplet size were altered solely as a result of being forced through sandstone cores, not because of fluids contacted within the core. The shear rate controlled whether the emulsion coalesced and produced no effluent emulsion, regenerated into an emulsion with larger droplets, or regenerated into an emulsion with smaller droplets. Oil recovery experiments showed that nanoparticle-stabilized oil-in-water emulsion increased the recovery of oil compared to a waterflood for cores with immobile and mobile oil. The mechanism is the coalesced oil droplets form a flowing phase that is miscible with oil present in the core and thus achieves a much more efficient displacement. The possible continuous generation and coalescence of droplets may have increased the apparent viscosity, improving the sweep efficiency of the emulsion injection. A novel oil recovery mechanism was shown in imbibition experiments where nanoparticle dispersion was used to displace oil. Large shear rates coupled with the affinity for nanoparticles at the oil water interface enabled residual oil to be mobilized, or for residual oil blobs to spawn smaller droplets that are stabilized by the nanoparticles and thus can be transported with the dispersion through the core.Item Modeling of nanoparticle transport in porous media(2012-08) Zhang, Tiantian; Bryant, Steven L.; Huh, Chun; Delshad, Mojdeh; Prodanovic, Masa; Johnston, Keith P.The unique properties of engineered nanoparticles have many potential applications in oil reservoirs, e.g., as emulsion stabilizers for enhanced oil recovery, or as nano-sensors for reservoir characterization. Long-distance propagation (>100 m) is a prerequisite for many of these applications. With diameters between 10 to 100 nanometers, nanoparticles can easily pass through typical pore throats in reservoirs, but physicochemical interaction between nanoparticles and pore walls may still lead to significant retention. A model that accounts for the key mechanisms of nanoparticle transport and retention is essential for design purposes. In this dissertation, interactions are analyzed between nanoparticles and solid surface for their effects on nanoparticle deposition during transport with single-phase flow. The analysis suggests that the DLVO theory cannot explain the low retention concentration of nanoparticles during transport in saturated porous media. Moreover, the hydrodynamic forces are not strong enough for nanoparticle removal from rough surface. Based on different filtration mechanisms, various continuum transport models are formulated and used to simulate our nanoparticle transport experiments through water-saturated sandpacks and consolidated cores. Every model is tested on an extensive set of experimental data collected by Yu (2012) and Murphy (2012). The data enable a rigorous validation of a model. For a set of experiments injecting the same kind of nanoparticle, the deposition rate coefficients in the model are obtained by history matching of one effluent concentration history. With simple assumptions, the same coefficients are used by the model to predict the effluent histories of other experiments when experimental conditions are varied. Compared to experimental results, colloid filtration model fails to predict normalized effluent concentrations that approach unity, and the kinetic Langmuir model is inconsistent with non-zero nanoparticle retention after postflush. The two-step model, two-rate model and two-site model all have both reversible and irreversible adsorptions and can generate effluent histories similar to experimental data. However, the two-step model built based on interaction energy curve fails to fit the experimental effluent histories with delay in the leading edge but no delay in the trailing edge. The two-rate model with constant retardation factor shows a big failure in capturing the dependence of nanoparticle breakthrough delay on flow velocity and injection concentration. With independent reversible and irreversible adsorption sites the two-site model has capability to capture most features of nanoparticle transport in water-saturated porous media. For a given kind of nanoparticles, it can fit one experimental effluent history and predict others successfully with varied experimental conditions. Some deviations exist between model prediction and experimental data with pump stop and very low injection concentration (0.1 wt%). More detailed analysis of nanoparticle adsorption capacity in water-saturated sandpacks reveals that the measured irreversible adsorption capacity is always less than 35% of monolayer packing density. Generally, its value increases with higher injection concentration and lower flow velocities. Reinjection experiments suggest that the irreversible adsorption capacity has fixed value with constant injection rate and dispersion concentration, but it becomes larger if reinjection occurs with larger concentration or smaller flow rate.Item Municipal economic growth through green projects and policies(2012-05) Lindner, Harry Dreyfus; Gamkhar, ShamaCities generally need economic growth. Green policies and projects are environmentally beneficial, desirable, expected by the public, and pragmatic in the long term. However, there is insufficient research on what, if any, municipal green projects and policies generate economic growth. To address this question, the author created a database of green and economic indicators, and modeled the green indicators to predict the economic indicators. The database included carbon usage, transportation metrics, water usage, the number of green jobs, and the gross domestic product (GDP) for the 100 largest cities, defined by metropolitan statistical area (MSA), in the U.S. To gather data on green indicators, existing green rankings, indices, and reports were evaluated for methodology and usability for this paper. The results of the data-gathering step show the need for more and better data collection. That means an increased number of green indicators should be collected, and data should be collected at the MSA (or county) level for more of the largest cities. Specifically to name some green indicators, data collection on energy usage, buildings, waste, land use, air quality, and food could be improved. Those green indicators would likely be included in a model that uses green indicators to predict green jobs or GDP. However, those were not included for the regressions in this paper. The results of the regressions in this paper show two indicators with promise for predicting economic growth as defined by GDP and number of green jobs: (1) percent of people using public transportation, biking, or walking to work, and (2) public water consumption per person. The first explanatory variable indirectly measures the adoption of policies that promote public transportation, biking, and walking. The results suggest that these policies have a positive effect on GDP and number of green jobs. This means the results suggest that as the percent increases, so does GDP and number of green jobs. The second explanatory variable measures the water conservation policies. The results suggest this variable has a negative, albeit weaker relationship with GDP per person. This means the results suggest as water conservation increases (less water usage per person), the GDP per person increases. This paper offers a methodology and some of the groundwork for building a model to show which, if any, municipal green projects and policies predict economic growth.Item Study of picosecond-scale electron dynamics in laser-produced plasmas with and without an external magnetic field(2013-12) McCormick, Matthew Warren; Ditmire, ToddThe interaction of ultra-short laser pulses and cluster targets can be used to explore a number of interesting phenomena, ranging from nuclear fusion to astrophysical blast waves. In our experiments, we focused on exploring very fast plasma dynamics of a plasma created by ionizing clusters and monomer gas. By using a 115 fs laser pulse, we can even study sub-picosecond plasma dynamics. In addition, we also wanted to impose an external magnetic field on these plasmas to study how the plasma evolution would change. The results of this work produced two significant results. First, a new, extremely fast ionization mechanism, with velocities as high as 0.5 c, was discovered which allows for significant plasma expansion on a picosecond time-scale. Experimental studies measured the velocity of the ionization wave, while particle-in-cell simulations helped explain the source and longevity of the wave. It was also observed that this ionization wave was not affected by the external magnetic field. Second, the external field was shown to inhibit plasma expansion on a time-scale of tens of picoseconds, which seems to be one of the first demonstrations of magnetic confinement on such a fast time-scale. Simple 1D simulations tell us that the field appears to slow electron heat transport in the plasma as well as inhibiting collisional ionization of electrons expanding into the surrounding gas. The inhibition of plasma expansion by the field on this time-scale may provide some evidence that magnetic confinement of a fusion plasma created by exploding clusters could improve the fusion yield by slowing heat loss as well as possibly electrostatically confining the hot ions.Item The Evolution of the Physicochemical Properties of Aerosols in the Atmosphere(2011-02-22) Tomlinson, JasonA Differential Mobility Analyzer/Tandem Differential Mobility Analyzer (DMA/TDMA) system was used to measure simultaneously the size distribution and hygroscopicity of the ambient aerosol population. The system was operated aboard the National Center for Atmospheric Research/National Science Foundation (NCAR/NSF) C-130 during the 2006 Megacity Initiative: Local and Global Research Observations (MILAGRO) field campaign followed by the 2006 Intercontinental Chemical Transport Experiment ? Phase B (INTEX-B) field campaign. The research flights for the MILAGRO campaign were conducted within the Mexico City basin and the region to the northeast within the pollution plume. The aerosol within the basin is dominated by organics with an average measured kappa value of 0.21 /- 0.18, 0.13 /- 0.09, 0.09 /- 0.06, 0.14 /- 0.07, and 0.17 /- 0.04 for dry particle diameters of 0.025, 0.050, 0.100, 0.200, and 0.300 mu m, respectively. As the aerosols are transported away from the Mexico City Basin, secondary organic aerosol formation through oxidation and condensation of sulfate on the aerosols surface rapidly increases the solubility of the aerosol. The most pronounced change occurs for a 0.100 mu m diameter aerosol where, after 6 hours of transport, the average kappa value increased by a factor of 3 to a kappa?of 0.29 /- 0.13. The rapid increase in solubility increases the fraction of the aerosol size distribution that could be activated within a cloud. The research flights for the INTEX-B field campaign investigated the evolution of the physicochemical properties of the Asian aerosol plume after 3 to 7 days of transport. The Asian aerosol within the free troposphere exhibited a bimodal growth distribution roughly 50 percent of the time. The more soluble mode of the growth distribution contributed between 67-80 percent of the overall growth distribution and had an average kappa?between 0.40 and 0.53 for dry particle diameters of 0.025, 0.050, 0.100, and 0.300 mu m. The secondary mode was insoluble with an average kappa?between 0.01 and 0.05 for all dry particle diameters. Cloud condensation nuclei closure was attained at a supersaturation of 0.2 percent for all particles within the free troposphere by either assuming a pure ammonium bisulfate composition or a binary composition of ammonium bisulfate and an insoluble organic.Item The Implementation of Photon Polarization into the Mercury Transport Code(2014-06-04) Windsor, EthanPolarization effects have been ignored in most photon transport codes to date, but new technology has created a need for portable, massively parallel, versatile transport codes that include the effects of polarization. In this project, the effects of both linear and elliptic polarization on the angular distribution of coherently and incoherently scattered photons are incorporated into the Monte Carlo transport code Mercury. In Mercury, photons are given a polarization fraction, polarization direction, and a polarization ellipticity. These new variables are tracked throughout each particle?s history. They impact and are impacted by interactions with the medium. The determination of how these variables affect the photon?s interactions with the medium uses Stokes vectors and the Mueller matrices for coherent and incoherent scattering events. Verification studies were performed comparing results from Mercury against analytical, experimental, and computational results. In all cases, Mercury showed agreement with the expected results. It was also shown that polarization effects are present and potentially significant even in cases where an initial beam is completely unpolarized. Adding polarization effects slowed the code between 10-50% depending on the particular problem. Mercury can now accurately model polarized light.Item Transport and retention of surface-modified nanoparticles in sedimentary rocks(2012-05) Yu, Haiyang; Bryant, Steven L.; Huh, ChunWith a number of advantages newly recognized, use of surface-coated nanoparticles is being proposed for various upstream oil applications, such as for Enhanced Oil Recovery or as nanosensors. The first requirement for many of these applications is the ability to transport the nanoparticles a desired distance from the injection well. It means the particles should exhibit little retention in sedimentary rocks and minimal formation damage. Also, a certain amount of particles should adsorb at target locations such as water/oil interfaces for response measurement, if they are used as nanosensors. Three kinds of nanoparticle dispersions are tested for coreflood experiment in sedimentary rock cores: silica nanoparticles, commercial iron-oxide nanoparticles, and in-house synthesized paramagnetic nanoparticles. The quantitative retention measurements from corefloods offer insight into the mechanisms for nanoparticle transport in various sedimentary rocks (Boise sandstone, layered-Berea sandstone and Texas Cream limestone), and also with and without oil in the core. The coreflood experiments helped to develop a procedure to identify efficiently a surface coating to a given nanoparticle, that will allow both long-term dispersion stability and long-distance transportability in a given reservoir rock. To achieve this objective, seventy-six coreflood experiments were conducted to investigate transport of nanoparticles at rock grain surface and at water/oil interface. The parameters analyzed in this dissertation are: dialysis of the nanoparticle dispersion; cross-linking of polymer on coating; hydrophobicity/hydrophilicity of surface coating; oil type; nanocluster size; flow velocity; pH; ionic strength; rock lithology; and injected nanoparticle concentration. Our results show that surface coating, ionic strength, and specific surface/interfacial area were dominant factors for nanoparticle retention at rock grain surface and water/oil interface. Nanoparticle retention concentration (adsorption density) at rock grain surface decreases with decrease in nanocluster size and increase in flow velocity. Some retained nanoparticles can be recovered by increasing flow velocity or decreasing ionic strength. It indicates that the nanoparticle retention at the rock grain surface is unlike the generally irreversible adsorption of surfactant or polymer molecules. Ionic strength affects both reversible and irreversible adsorption of nanoparticles at rock grain surface; in these corefloods the irreversible retention is mainly due to the instability of nanoparticle dispersion and subsequent aggregation under high salinity conditions. The nanoparticle synthesis method, whether dialyzed or not, and cross-linking of coating polymer, all have significant impact on dispersion stability, especially for aqueous dispersion with high ionic strength. Nanoparticle adsorption at water/oil interface can be increased by increasing hydrophobicity of surface coating, or to a certain extent by increasing ionic strength of dispersion.